- A
The MTU settings on the on-premises router and the AWS Direct Connect interface.
MTU mismatch can cause intermittent connectivity issues, especially with DMS.
- B
The route table of the VPC to ensure it has a route to the on-premises CIDR via the Direct Connect virtual interface.
Why wrong: If routing were missing, it would fail consistently, not intermittently.
- C
The VPN connection status as a backup path.
Why wrong: Only Direct Connect is used, no VPN.
- D
The security group of the RDS instance to ensure it allows traffic from the on-premises IP range.
Why wrong: Security groups are for VPC resources, but the issue is intermittent, not consistent blocking.
Question 504 of 1,705
ANS-C01 MTU (Maximum Transmission Unit) Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: mTU (Maximum Transmission Unit). Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is using AWS Database Migration Service (DMS) to replicate data from an on-premises Oracle database to an Amazon RDS for Oracle instance. The replication is failing intermittently with connection timeouts. The network connectivity uses a Direct Connect private VIF. What should the network team investigate first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The MTU settings on the on-premises router and the AWS Direct Connect interface.
Correct answer: Option A is correct because MTU mismatch between the on-premises router and AWS Direct Connect interface can cause packet fragmentation or drops, leading to intermittent connection timeouts. The default MTU for Direct Connect is 1500 bytes, but if the on-premises router uses a larger MTU (e.g., 9001 for jumbo frames), packets may be dropped or fragmented, causing timeouts. Option B is incorrect because routing misconfiguration would cause persistent failure, not intermittent. Option C is incorrect because a VPN is not used as a primary path when Direct Connect is available. Option D is incorrect because security groups apply to traffic within the VPC, not to on-premises traffic over Direct Connect.
Key principle: MTU (Maximum Transmission Unit)
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The MTU settings on the on-premises router and the AWS Direct Connect interface.
- ✗
The route table of the VPC to ensure it has a route to the on-premises CIDR via the Direct Connect virtual interface.
Why it's wrong here
If routing were missing, it would fail consistently, not intermittently.
- ✗
The VPN connection status as a backup path.
Why it's wrong here
Only Direct Connect is used, no VPN.
- ✗
The security group of the RDS instance to ensure it allows traffic from the on-premises IP range.
Why it's wrong here
Security groups are for VPC resources, but the issue is intermittent, not consistent blocking.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- MTU (Maximum Transmission Unit)
- AWS Direct Connect
- Packet Fragmentation
- Intermittent Connectivity Issues
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
MTU (Maximum Transmission Unit)
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review mTU (Maximum Transmission Unit), then practise related ANS-C01 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Management and Operations — This question tests Network Management and Operations — MTU (Maximum Transmission Unit).
What is the correct answer to this question?
The correct answer is: The MTU settings on the on-premises router and the AWS Direct Connect interface. — Correct answer: Option A is correct because MTU mismatch between the on-premises router and AWS Direct Connect interface can cause packet fragmentation or drops, leading to intermittent connection timeouts. The default MTU for Direct Connect is 1500 bytes, but if the on-premises router uses a larger MTU (e.g., 9001 for jumbo frames), packets may be dropped or fragmented, causing timeouts. Option B is incorrect because routing misconfiguration would cause persistent failure, not intermittent. Option C is incorrect because a VPN is not used as a primary path when Direct Connect is available. Option D is incorrect because security groups apply to traffic within the VPC, not to on-premises traffic over Direct Connect.
What should I do if I get this ANS-C01 question wrong?
Review mTU (Maximum Transmission Unit), then practise related ANS-C01 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
MTU (Maximum Transmission Unit)
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Last reviewed: Jun 20, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.
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